Is it true that you can collect ei while under employed?

I've only collected ei when my old company went bankrupt during covid lockdown. My current company is really struggling under trumps tariffs. These days I'm only 20 hours a week some week I don't get any hours at all. I heard from somebody that people in my shoes can qualify for ei.

Is it true? If so would I need a request something from the hr department of my company for the application?